I just started using a MacBook Pro in addition to my Windows 7 laptop (to see if the OS X 10.8 will be a good alternative for me). At Windows bootup, since my user is the only one on the computer, it is already selected at the login screen and I just type my password and go.

On OS X 10.8.2 it shows my name and a Guest account. I have to select my name with the mouse before I can type in my password. I can't even use the keyboard to tab over to my name:

How can I disable the Guest account from showing on the login screen so only my user is displayed with a password box?

In Users & Groups the Guest user is disabled:

I also did some searching and found that this could be a side affect of the 'Find my Mac' feature of iCloud. I verified it is also disabled:

This turned out to be correct. I didn't realize "Other" and "Guest" were separate (I just assumed enabling Guest meant the Other option showed up to enter Guest credentials). The ultimate reason for the "Other" option turned out to be a group that was added by some software (Puppet) that I am working with. I installed it locally and it had installed a puppet user and puppet group. After uninstalling the software and removing the users, the login screen now shows only my user with the password box. Thanks!
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Andy ShinnMar 14 '13 at 15:50

You are welcome! I could only do that since you took the time to get a photograph of your display. I took me a while to look closer and to be honest I was distracted by the Rubber Ducky on the top left of the display :)
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user44516Mar 15 '13 at 14:56

I was able to confirm this being tied to "Find My Mac" being enabled by toggling the option while setting up a new Mac, however I'm unable to revert back to the previous state where the only options are normal user accounts. I've disabled "Find My Mac", signed out of iCloud, rebooted, removed com.apple.loginwindow.plist from /Library all with no change.

What I CAN tell you is that you can login without needing to use the trackpad/mouse:

At the login window you can use the right or left arrow keys to select a user

Ah, I didn't think of using the arrow keys. This helps. But doesn't seem like the ultimate solution. If I can't find a real fix in a week or so, I will accept this as an answer which should gain you some rep so you can add comments in the future :)
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Andy ShinnMar 11 '13 at 17:18

I totally get that. Once I have some free time at work (Ha!) I'll see if I can figure it out, if nothing else because it's an odd bug.
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Mr RabbitMar 11 '13 at 18:57

From the Apple menu choose System Preferences....
From the View menu choose Users & Groups.
Click on the lock and authenticate with an administrator account.
Click Login Options....
Click the "Edit..." or "Join..." button at the bottom right
Click the "Open Directory Utility..." button.
Click the lock in the Directory Utility window.
Enter an administrator account name and password, then click OK.
Choose Disable Root User from the Edit menu.

Just in case you are wondering: You are NOT the root user.

About the root user

The user named "root" is a special user in UNIX-style operating systems that has read and write privileges to all areas of the file system. The root user should only be used for specific administration or monitoring tasks. After completing a task as the root user, you should log out of Mac OS X (this is what your IT forgot to do) and log back in using a normal or administrator account. You should disable root access if you do not use it often.